Firing valve

ABSTRACT

A firing valve for charging a load with compressed gas, such as air, is disclosed in which admission of compressed gas from a source to the valve displaces a piston against the restraint of a dashpot so as to open a passageway from the source to the load at a controlled rate. During charging, a second piston, slideable with respect to the first, is displaced to block a venting passageway but unblocks this passageway during retraction when the system is to be discharged.

United States Patent [191 Hayner et al.

[ May 22, 1973 [54] FIRING VALVE [75] Inventors: Paul F. Hayner, Lexington, Mass;

Edgar R. Beruier, Nashua, NH,

Assignee: Sanders Associates, Inc., Nashua,

Filed: Apr. 3, 1972 Appl. No.: 240,607

US. Cl ..137/596.l, l37/625.68 Int. Cl ..F16k 11/00 Field of Search ..l37/596.l, 625.26,

[56] References Cited UNITED STATES PATENTS 2,727,761 12/1955 Elliott et al. ..l37/625.68 X

Ill/ll l//// 7/1960 Vander Kaay ..l37/596.1 X 1/1963 Schulz ..l37/596.l X

Primary Examiner-Henry T. Klinksiek Assistant ExaminerRobert J. Miller Att0mey-Louis Etlinger [57] ABSTRACT A firing valve for charging a load with compressed gas, such as air, is disclosed in which admission of compressed gas from a source to the valve displaces a piston against the restraint of a dashpot so as to open a passageway from the source to the load at a controlled rate. During charging, a second piston, slideable with respect to the first, is displaced to block a venting passageway but unblocks this passageway during retraction when the system is to be discharged.

8 Claims, 1 Drawing Figure PATENTEU HAY22|915 momnow FIRING VALVE FIELD OF THE INVENTION This invention relates generally to pneumatic valves and particularly to so-called firing valves which are required to admit a compressed gas, such as air, from a source to a load at an automatically controlled rate.

BACKGROUND OF THE INVENTION Projectiles are frequently expelled from a housing, such as a gun barrel, and given impetus by the force of compressed air or other gas which is obtained from a source of such gas under pressure and admitted to a chamber at the rear of the projectile. One of the problems associated with firing a projectile by such an arrangement is that the air must be admitted to the chamber slowly enough to prevent damage to the projectile and its housing and to insure a smooth ejection yet fast enough to expel the projectile with sufficient velocity and avoid excessive waste of time. One known kind of firing valve which has been widely used includes a piston slideable in a hollow cylinder. Air from the source is admitted to the cylinder so as to act on the end of the piston which advances against adashpot at the other end of the cylinder. When the piston has advanced a short distance, a passageway is opened, through restric' tors, from the source to the load port, to which. air flows. At the same time, a first port in the piston connects the load port to a chamber formed within the pis ton itself and a second port connects this chamber to atmosphere through another set of restrictors. Thus, at this stage of operations, some of the air from the source flows to the load while some is exhausted to the atmosphere. The piston continues to advance and a short time later closes the passageways between the load port and the interior chamber and between the interior chamber and the atmosphere so that the piston then advances, impeded only by the dashpot. All of the air admitted to the hollow cylinder then flows to the load. After the projectile has been fired, air is admitted to the opposite end of the piston which in retracting again connects the load to the atmosphere thereby discharging the load chamber in preparation for subsequent operations.

Although firing valves such as briefly described above have been widely used, they have been subject to certain disadvantages. It has been found that in many cases air is admitted to the load too slowly. Also, the venting of gas to the atmosphere is wasteful of the energy of the compressed air in the source. Additionally, the venting of large amounts of gas causes a lot of unwanted noise.

It is a general object of the present invention to provide an improved firing valve.

Another object is to provide a firing valve which enables the load chamber to recharge more quickly.

Yet another object is to provide a firing valve which is quiet in operation.

SUMMARY OF THE INVENTION Briefly stated, a firing valve incorporating the present invention is similar to previously known firing valves, such as the one briefly described above, except that the piston is formed in two parts. The first part includes the land which variably exposes the load port to the source of pressure. The second part includes the interior chamber and the sets of apertures which connect this chamber to the load port and to the atmosphere. As the piston is first displaced, air reaching the load port is immediately transmitted to the interior of the chamber as before. However, it now acts against the wall of the chamber remote from the first land thereby displacing the second part of the piston rapidly away from the first portion to a position at which the passageway to the atmosphere is blocked. Thus, all of the air admitted from the source now goes to the load, none is wasted through venting to the atmosphere, and the noise due to venting is eliminated.

DESCRIPTION OF PREFERRED EMBODIMENT For a clearer understanding of the invention, reference may be made to the following detailed description and the accompanying Drawing, the single FIGURE of which is a schematic cross sectional diagram of a firing valve incorporating the present invention together with the external connections.

Referring now to the Drawing, the firing valve includes a valve housing 1 1, preferably made in a number of parts in accordance with well known practice, but herein denoted generally by the single reference character 11. The housing 11 is formed to define a hollow cylinder 12 and also to define a reduced diameter passageway l3 coaxial with the cylinder 12 and extending from the interior of the cylinder at the right end thereof to the exterior of the housing. The passageway 13 is connected by means of a conduit 14 to a shut off valve 15 which in turn is connected by means of another conduit 16 to a source 17 of air under pressure-Positioned within the hollow cylinder 12 is a first piston denoted generally by the reference character 18 and including a land 18a. In the reference position of the piston 18 as shown in the drawing, the right end thereof blocks the reduced diameter passageway 13. The housing 11 is also formed to define a generally annular groove 19 in the exterior of the cylinder 12 near the right end thereof as shown in the drawing. The groove 19 includes a portion 19a which extends to the exterior of the housing and is connected by means of a conduit 21 to a load device 22. The latter may, for example, be the chamber to which compressed air is admitted for the purpose of expelling a projectile. The groove 19 is positioned with respect to the passageway 13 and the reference position of the piston 18 so that a small displacement of this piston to theleft from its reference position establishes communication between the passageway 13 and the groove 19. The portion of the groove 19 through which such communication is established is preferably filled with a plurality of fluid resistors or restrictors such as a wire mesh, smalldiameter tubes or, preferably, a plurality of discs having baffles on one face thereof and stacked together so as to form many small series and parallel connected passageways extending radially outward from groove 19.

The piston 18 also includes a smaller diameter, rodlike portion 18b, which is fastened to the land 18 and extends along the axis of the cylinder 12 toward the second end thereof. Near this end, the rod-like portion 18b has fastened thereto a dash plate 22 in such position as to lie within a chamber 23 which chamber is in effect a larger diameter portion of the cylinder 12. The chamber 23 is filled with oil and the body 11 is formed to define a passageway 24 connecting those portions of this chamber which lie at opposite sides of the plate 22.

the cylinder 12 to the An adjustable fluid resistor 25 is positioned within the chamber 24. The plate 22 is formed with a number of holes therethrough which are normally covered by another plate 26 which is urged into engagement with the left side thereof by a spring 27. The left end of the rodlike portion 18b is preferably held by a substantially fluid tight sliding fit in the left end wall of the housing 11. The assemblage just briefly described constitutes a dashpot which restricts the movement of the piston 18 to the left from the reference position shown in the Drawing while leaving its return movement to the right substantially unimpeded.

The housing 11 is also formed to define a radial passageway from the interior of the cylinder 12 to the exterior of the housing 11. This passageway is located between the groove 19 and the chamber 23. It is preferably filled with a number of fluid restrictors, preferably comprising a stack of plates with baffles on one side similar to the restrictors 21.

A second piston 33 is positioned within the cylinder 12 engaging the interior of that cylinder and slideable along the rod-like portion 18b. The piston 33 is shown in its reference position and, in this position, it extends from engagement with the land 18a to a point to the left of the passageway 31 and restrictors 32. It is urged toward this reference position by a spring 34. A stop member 35 limits the movement of the piston 33 in the leftward direction. The piston 33 is formed to define an in interior chamber 36 which surrounds the rod-like portion 18b and is in communication with the interior of the cylinder at the right end adjacent the land 18a. The left end of the piston 33 is in substantially fluid tight sliding engagement with the rod-like portion 18b. The wall of the piston 33 is formed to define one or more apertures 37 extending through the wall in such position that, in the reference position shown, the chamber 36 is in communication with groove 19. The wall of the piston 33 is also formed to define one or more apertures 38 positioned so that, in the reference position shown, the chamber 36 is in communication with the radial passageway 31. The piston 33, the apertures 37 and 38, the distance between these apertures, and the location of the stop member 35 are selected so that when the piston 33 is displaced to the left and engages the stop member 35 the portion of the wall of the piston between the apertures 37 and 38 blocks the radial passageway 31.

l The housing 11 is also formed to define a passageway 41 extending from the interior of the cylinder 12 at a point to the left of the piston 33 to the outside of the housing 11 where it is connected to a conduit 42 which in turn is connected to the outlet of a valve 43 the inlet of which is connected by means of a conduit 44 to the source 17 of air under pressure.

The firing valve is shown in the drawing in its reference, or standby position. The spring 34 is of sufficient strength to hold the piston 33 up against the land 18a in the absence of substantial forces tending to displace it to the left but is quite weak indeed compared to the pneumatic forces encountered during operation. At this time both the valve and the valve 43 are closed so that no air is applied to the firing valve. When it is desired to charge the load 22 with compressed air at the controlled rate previously mentioned, the valve 15 is opened thereby admitting compressed air through the conduit 14 and the passageway 13 so as to act on the right side of the land 18a. The piston 18 is soon displaced slightly to the left, pushing the piston 33 ahead of it but restrained by the dashpot fastened to the rodlike portion 18b. The piston 18 need move but a short distance to the left before air will flow over the land 18 and into the groove 19 and through the conduit 21 to the load 22. At the same time air will flow through the apertures 37 to the chamber 36. Although the chamber 36 is in communication with the radial passageway 31, which is open to the atmosphere, the right side of the chamber 36 is substantially open while the left side is closed. Accordingly, the excess pressure within the chamber 36 is sufficient to move the piston 33 rapidly against the urging of the spring 34 into engagement with the stop 35. At this time, the piston 33 blocks the radial passageway 31 so that all of the air entering the groove 19 goes to the load 22. The piston 18 continues to travel to the left at a rate determined by the characteristics of the dashpot which can be adjusted by varying the adjustable restrictor 25. As the piston 18 moves to the left, more and more air is admitted to the load 22. At the conclusion of the operation, the piston 18 has moved all the way to the left and the land 18a is again in engagement with the piston 33 although both are displaced to the left from the position shown in the Drawing. In this position, the land 18a is in such a position that fluid can flow to the load 22 from the conduit 14 only by passing through the restrictors 21. The valve 15 may then be shut off.

In order to restore initial conditions, the valve 43 is opened thereby admitting air through the passageway 41 to the left side of the piston 33. The piston 33 need move only a short distance to the right before the apertures 38 again establish communication between the chamber 36 and the radial passageway 31 and the apertures 37 again establish communication between the chamber 36 and the groove 19. Thus, the load 22 is vented to atmosphere, both pistons are returned to their reference positions, initial conditions are restored and the valve 43 may be closed.

It is to be noted that during operation very little air is vented through the passageway 31 because the piston 33 is displaced to the left and blocks off this passageway almost immediately. Therefore, no compressed air is wasted, substantially all of it going to the load. Accordingly, the load 22 can be charged much more quickly since none of the air is wasted. The rate of charging can be controlled by adjusting the characteristics of the dashpot. It is also to be noted that the elimination of the venting of gas to atmosphere also eliminates the noise associated with such venting.

Although a preferred embodiment of the invention has been described in considerable detail for illustrative purposes, many modifications will occur to those skilled in the art. It is therefore desired that the protection afforded by Letters Patent be limited only by the true scope of the appended claims.

What is claimed is:

1. A firing valve for charging a load with compressed gas at a controlled rate comprising a housing formed to define a hollow cylinder and also formed to define an annular groove in said cylinder and a first passageway connecting said groove to the exterior of said housing for connection to said load, a piston including a land disposed within said cylinder, said housing being formed to define a second passageway for connection to a source of gas under pressure and communicating with one end of said land, said piston having a reference position at which said land blocks communication from said second passageway to said first passageway and being displaceable therefrom in a first direction by action of said gas to variably unblock such communication, a dashpot connected to said piston for restraining displacement thereof in said first direction, said housing also being formed to define a third passageway establishing communication between the interior of said cylinder and the exterior of said housing, characterized in that said valve includes an auxiliary piston, slideable with respect to the aforesaid piston having a reference position in engagement with said land and positioned within said cylinder so as to be subjected to pressure of the gas in said first passageway so as to be urged thereby away from said reference position toward a position at which it blocks said third passageway.

2. A firing valve in accordance with claim 1 which includes a spring mounted so as to urge said second piston toward its reference position.

3. A firing valve in accordance with claim 1 in which said reference position of said second piston is that position at which it engages said land while said land is in its reference position.

4. A firing valve in accordance with claim 1 in which means are provided for admitting gas under pressure to said cylinder so as to urge both of said pistons toward their reference positions.

5. A firing valve in accordance with claim 1 which includes a stop member for limiting the movement of said second piston away from its reference position to a position at which said third passageway is blocked.

6. A firing valve comprising a housing formed to define a hollow cylinder, a piston within said cylinder including a land engaging the interior of said cylinder, said piston having a reference position adjacent a first end of said cylinder, said housing being formed to define a reduced diameter passageway coaxial with said cylinder and extending from the interior of said cylinder at the first end thereof to the exterior of said housing, said reduced diameter passageway being blocked by said land when said piston is in said reference position, said passageway being for connection to a source of fluid under pressure, said housing being formed to define an annular groove in the exterior of said cylinder including a portion extending to the exterior of said housing for connection to a load device, said groove being positioned so that displacement of said land away from its reference position establishes communication between said passageway and said groove, said piston including a smaller diameter rod-like portion fastened to said land and extending along the axis of said cylinder toward the second end thereof, said rod-like portion being connected to actuate a dashpot located adjacent said second end of said cylinder, said housing also being formed to define a radial passageway extending from the interior of said cylinder intermediate its ends to the exterior of said body, characterized in that said valve includes an auxiliary piston engaging the interior of said cylinder and slideable on said rod-like portion, a spring disposed to urge said auxiliary piston towards said first end of said cylinder to a reference position at which it engages said land, said auxiliary piston being formed to define an interior chamber surrounding said rod-like portion and communicating with the interior of said cylinder at that end adjacent to said land, said auxiliary piston being formed to be in sealing engagement with said rod-like portion at the opposite end thereof, said auxiliary piston being formed to define first and second apertures positioned so that when said auxiliary piston is in said reference position said apertures communicate with said annular groove and with said radial passageway respectively and both communicate with said chamber, said auxiliary piston also being formed and said apertures spaced so that when said auxiliary piston is displaced a predetermined distance from said reference position, said radial passageway is blocked, whereby when fluid under pressure is admitted to said reduced diameter passageway said land is tons toward their reference positions. 

1. A firing valve for charging a load with compressed gas at a controlled rate comprising a housing formed to define a hollow cylinder and also formed to define an annular groove in said cylinder and a first passageway connecting said groove to the exterior of said housing for connection to said load, a piston including a land disposed within said cylinder, said housing being formed to define a second passageway for connection to a source of gas under pressure and communicating with one end of said land, said piston having a reference position at which said land blocks communication from said second passageway to said first passageway and being displaceable therefrom in a first direction by action of said gas to variably unblock such communication, a dashpot connected to said piston for restraining displacement thereof in said first direction, said housing also being formed to define a third passageway establishing communication between the interior of said cylinder and the exterior of said housing, characterized in that said valve includes an auxiliary piston, slideable with respect to the aforesaid piston having a reference position in engagement with said land and positioned within said cylinder so as to be subjected to pressure of the gas in said first passageway so as to be urged thereby away from said reference position toward a position at which it blocks said third passageway.
 2. A firing valve in accordance with claim 1 which includes a spring mounted so as to urge said second piston toward its reference position.
 3. A firing valve in accordance with claim 1 in which said reference position of said second piston is that position at which it engages said land while said land is in its reference position.
 4. A firing valve in accordance with claim 1 in which means are provided for admitting gas under pressure to said cylinder so as to urge both of said pistons toward their reference positions.
 5. A firing valve in accordance with claim 1 which includes a stop member for limiting the movement of said second piston away from its reference position to a position at which said third passageway is blocked.
 6. A firing valve comprising a housing formed to define a hollow cylinder, a piston within said cylinder including a land engaging the interior of said cylinder, said piston having a reference position adjacent a first end of said cylinder, said housing being formed to define a reduced diameter passageway coaxial with said cylinder and extending from the interior of said cylinder at the first end thereof to the exterior of said housing, said reduced diameter passageway being blocked by said land when said piston is in said reference position, said passageway being for connection to a source of fluid under pressure, said housing being formed to define an annular groove in the exterior of said cylinder including a portion extending to the exterior of said housing for connection to a load device, said groove being positioned so that displacement of said land away from its reference position establishes communication between said passageway and said groove, said piston including a smaller diameter rod-like portion fastened to said land and extending along the axis of said cylinder toward the second end thereof, said rod-like portion being connected to actuate a dashpot located adjacent said second end of said cylinder, said housing also being formed to define a radial passageway extending from the interior of said cylinder intermediate its ends to the exterior of said body, characterized in that said valve includes an auxiliary piston engaging the interior of said cylinder and slideable on said rod-like portion, a spring disposed to urge said auxiliary piston towards said first end of said cylinder to a reference position at which it engages said land, said auxiliary piston being formed to define an interior chamber surrounding said rod-like portion and communicating with the interior of said cylinder at that end adjacent to said land, said auxiliary piston being formed to be in sealing engagement with said rod-like portion at the opposite end thereof, said auxiliary piston being formed to define first and second apertures positioned so that when said auxiliary piston is in said reference position said apertures communicate with said annular groove and with said radial passageway respectively and both communicate with said chamber, said auxiliary piston also being formed and said apertures spaced so that when said auxiliary piston is displaced a predetermined distance from said reference position, said radial passageway is blocked, whereby when fluid under pressure is admitted to said reduced diameter passageway said land is displaced thereby admitting fluid to said groove and to said chamber and urging said auxiliary piston towards said second end of said cylinder.
 7. A firing valve in accordance with claim 6 which includes a stop member for limiting the displacement of said auxiliary piston to a predetermined distance from its reference position at which it blocks said radial passageway.
 8. A firing valve in accordance with claim 6 in which means are provided for admitting gas under pressure to said cylinder in such location as to urge both of said pistons toward their reference positions. 